Abstract:  In this discussion, we will present some background to the EnV-S analysis and a case example - in the destruction of PFC's from etch tools.

Given the economic relevance of the semiconductor industry and the rapid rate of change, it is important to examine the environmental impacts of processing, including life cycle effects.  In this presentation, we first perform a quick environmental analysis of semiconductor manufacturing using current, publicly available databases.  This includes first order 'top-down' life cycle analysis using Economic Input Output Life Cycle Assessment (EIOLCA) methods.

Gaps in such analysis (uncertainties, the ability to effect change, the lack of consistent metrics, etc) leads on to a discussion on a 'bottom-up' Design for Environment (DFE) tool, the EnV-S, that has been developed to facilitate inclusion of specific environmental factors in equipment design/selection and process decisions.  The main metric to compare environmental factors is an environmental cost of ownership metrics.  Other metrics used include process-specific environmental factors (such as water, energy use), manufacturing performance factors (uptime, reliability) and health factors (multi-criteria hazard analysis).    In this presentation, we will focus on the use of the EnV-S to enable comparative analysis of technologies to destroy PFC's from dielectric etch tools.

The presentation will conclude with ideas for future work - to bridge the gap between bottom-up and top-down analysis by linking up specific EnV-S approach with broader supply chain and life-cycle factors.  A proposed avenue of research will involve using the EnV-S (i)  in conjunction with Economic Input Output (EIO) approaches and (ii)  with SETAC style life cycle approaches to develop a hybrid analysis. (PDF)

Abstract:  We have previously investigated components of mass balance (reactant utilization), energy consumption (wafer heating), and manufacturing cycle time using a dynamic simulation of the Cu CVD unit process as a prototype system.  The simulator is based on a physical model of the process and equipment, and captures the essential dynamic behaviors as well as the time-integrated behaviors through the process cycle. We have since expanded and enhanced these studies to obtain a more comprehensive picture of the

important factors in these metrics.  We have incorporated energy costs associated with pumping equipment and other components along with the previously treated wafer heating component of energy usage in the Cu CVD process.  In fact, pumping systems not only consume more energy than wafer heating and other factors, but their energy usage varies considerably depending on the details of the pump types chosen, both in average power through the process cycle and in dynamic power fluctuations that occur during key transitions of the process cycle.  Accordingly, there may be real ESH benefit in working closely with component supplies to choose components that are adequate to the product performance and manufacturing cost metrics, and at the same time beneficial to ESH metrics. In addressing mass balance from the perspective of reactant utilization and its relation to process cycle time as a function of pressure, temperature, and gas flow rates, both win-win and trade-off situations emerge.  The former is easy to treat, but a more careful analysis methodology is needed to manage tradeoff situations.  We have begun to outline an approach to this challenge which includes

consideration of manufacturing cost components and also linkages to ESH impacts beyond the factory. (PDF)